Summary: Astronomy & Astrophysics manuscript no. 3687eos c ESO 2006
April 21, 2006
Magnetoacoustic wave propagation in off-limb polar regions
E. O'Shea1, D. Banerjee2, and J.G.Doyle1
1
Armagh Observatory, College Hill, Armagh BT61 9DG, N.Ireland
e-mail: eos@arm.ac.uk, e-mail: jgd@arm.ac.uk
2
Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560 034, India
e-mail: dipu@iiap.res.in
ABSTRACT
Aims. To find evidence of magnetoacoustic waves in off-limb polar regions.
Methods. Using temporal series data from the Coronal Diagnostic Spectrometer (CDS) on SOHO, we study oscillations found in radiant flux
and velocity measurements from transition region and coronal spectral lines. We use Fourier techniques to measure phase delays between flux
(`intensity') oscillations and between velocity oscillations of different transition region-corona and corona-corona line pairs. We also measure
the phase delays between flux and velocity oscillations (I-V).
Results. The phase delays measured between different line pairs, when plotted over a ­180
to +180
range, line up along diagonal lines
corresponding to measurable and fixed time delays. The slopes of these diagonal lines suggest the outward propagation of waves. Using the